lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <8f0df756-4f71-9d96-7a52-45bf51482556@sandeen.net> Date: Wed, 17 Jun 2020 12:55:24 -0500 From: Eric Sandeen <sandeen@...deen.net> To: "Darrick J. Wong" <darrick.wong@...cle.com> Cc: "J. Bruce Fields" <bfields@...ldses.org>, Christoph Hellwig <hch@...radead.org>, Masayoshi Mizuma <msys.mizuma@...il.com>, Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, Alexander Viro <viro@...iv.linux.org.uk>, Masayoshi Mizuma <m.mizuma@...fujitsu.com>, linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-xfs <linux-xfs@...r.kernel.org> Subject: Re: [PATCH] fs: i_version mntopt gets visible through /proc/mounts On 6/17/20 12:24 PM, Darrick J. Wong wrote: > On Wed, Jun 17, 2020 at 12:14:28PM -0500, Eric Sandeen wrote: >> >> >> On 6/17/20 10:58 AM, J. Bruce Fields wrote: >>> On Wed, Jun 17, 2020 at 01:03:14AM -0700, Christoph Hellwig wrote: >>>> On Tue, Jun 16, 2020 at 04:21:23PM -0400, Masayoshi Mizuma wrote: >>>>> From: Masayoshi Mizuma <m.mizuma@...fujitsu.com> >>>>> >>>>> /proc/mounts doesn't show 'i_version' even if iversion >>>>> mount option is set to XFS. >>>>> >>>>> iversion mount option is a VFS option, not ext4 specific option. >>>>> Move the handler to show_sb_opts() so that /proc/mounts can show >>>>> 'i_version' on not only ext4 but also the other filesystem. >>>> >>>> SB_I_VERSION is a kernel internal flag. XFS doesn't have an i_version >>>> mount option. >>> >>> It probably *should* be a kernel internal flag, but it seems to work as >>> a mount option too. >> >> Not on XFS AFAICT: >> >> [600280.685810] xfs: Unknown parameter 'i_version' > > Yeah, because the mount option is 'iversion', not 'i_version'. Even if unless you're ext4: {Opt_i_version, "i_version"}, ok "iversion" is what mount(8) takes and translates into MS_I_VERSION (thanks Darrick) # strace -vv -emount mount -oloop,iversion fsfile mnt mount("/dev/loop0", "/tmp/mnt", "xfs", MS_I_VERSION, NULL) = 0 FWIW, mount actually seems to pass what it finds in /proc/mounts back in on remount for ext4: # strace -vv -emount mount -o remount mnt mount("/dev/loop0", "/tmp/mnt", 0x55bfcbdca150, MS_REMOUNT|MS_RELATIME, "seclabel,i_version,data=ordered") = 0 but it still looks unhandled on remount. Perhaps if /proc/mounts exposed "iversion" (not "i_version") then mount -o remount would DTRT. -Eric > you were going to expose the flag state in /proc/mounts, the text string > should match the mount option. > >> so we can't be exporting "mount options" for xfs that aren't actually >> going to be accepted by the filesystem. >> >>> By coincidence I've just been looking at a bug report showing that >>> i_version support is getting accidentally turned off on XFS whenever >>> userspace does a read-write remount. >>> >>> Is there someplace in the xfs mount code where it should be throwing out >>> SB_I_VERSION? >> >> <cc xfs list> >> >> XFS doesn't manipulate that flag on remount. We just turn it on by default >> for modern filesystem formats: >> >> /* version 5 superblocks support inode version counters. */ >> if (XFS_SB_VERSION_NUM(&mp->m_sb) == XFS_SB_VERSION_5) >> sb->s_flags |= SB_I_VERSION; >> >> Also, this behavior doesn't seem unique to xfs: >> >> # mount -o loop,i_version fsfile test_iversion >> # grep test_iversion /proc/mounts >> /dev/loop4 /tmp/test_iversion ext4 rw,seclabel,relatime,i_version 0 0 >> # mount -o remount test_iversion >> # grep test_iversion /proc/mounts >> /dev/loop4 /tmp/test_iversion ext4 rw,seclabel,relatime 0 0 >> # uname -a >> Linux <hostname> 5.7.0-rc4+ #7 SMP Wed Jun 10 14:01:34 EDT 2020 x86_64 x86_64 x86_64 GNU/Linux > > Probably because do_mount clears it and I guess xfs don't re-enable > it in any of their remount functions...
Powered by blists - more mailing lists